Objective The on-board charger is a core component of the auxiliary power supply system for Type D suburban trains. In daily operation, abnormal intermediate voltage faults of the charger occur frequently, seriously affecting the normal operation of suburban lines. Therefore, it is necessary to identify the root cause of these faults and carry out rectification research.

Method Taking the on-board charger of Type D suburban trains as the research object, the overall electrical control principle of the charger is elaborated. Four main triggering factors of the abnormal intermediate voltage faults in the charger are analyzed, and the root cause is identified. The specific causes of the fault are analyzed in detail. Combined with actual on-site operating conditions and environmental monitoring data, special tests are carried out. By means of hierarchical troubleshooting and section-by-section verification, fault troubleshooting and analysis are conducted on the voltage sensor power supply, signal acquisition, coil structure, and other aspects. Finally, targeted countermeasures are proposed to address the causes of the fault.

Result & Conclusion  High-frequency pulse interference signals generated by the complex electromagnetic environment along the line lead to inter-turn short circuits in the coil of the intermediate voltage sensor, which is the primary cause of abnormal voltage readings. Alternative sensors with better temperature resistance and voltage withstand performance are adopted according to the on-site electromagnetic environment to effectively avoid equipment faults induced by high-frequency electromagnetic interference. Although only the enameled wire specification is changed in the improved voltage sensor, compared with the original version, the optimized sensor exhibits approximately doubled enamel film thickness, a temperature index increase of about 30℃ and a breakdown voltage rise of 1.538 kV.